1. Field of the Invention
The present invention relates to apparatus and methods for paving, and in particular, to paving by laying down a plurality of discrete elements.
2. Description of Related Art
Paving outdoor surfaces requires relatively heavy materials that can withstand the elements outdoors. Consequently, conventional outdoor paving techniques require one to transport and lay many hundreds, if not thousands, of pounds of paving material, which becomes a serious logistical challenge.
Stones, bricks, and other masonry articles have been used to pave walkways, streets, patios, etc. Cobblestones are an early example. A more recent example is the use of paving bricks or pavers. As shown in FIG. 8, an earthen surface can be prepared by placing a layer of gravel 10 in a shallow excavation. Gravel layer 10 will be compacted in the usual fashion. The region to be paved is encompassed by border elements, in this case wooden beam 12, although in some cases the edge restraint may be a vertical plastic strip with a lower ledge (not shown) designed to slip under the paving bricks. Gravel layer 10 is covered with a layer of sand 14. Solid paving bricks P are laid atop sand layer 14 in a pleasing pattern, with some arranged transverse to the others. A gap is left between paving bricks P, which is filled with sand S that permits water drainage through layers 14 and 10 to the earth E below.
Laying paving bricks P is time-consuming since one must be careful to maintain a uniform gap between bricks, lay the bricks in a pattern that is pleasing, and in some cases choose a sequence of differently colored bricks to produce a pleasant appearance.
Known composite materials are used as a replacement for wood. These composites may include a plastic material with cellulosic filler such as wood flour, wood chips, comminuted coconut or peanut shells, etc. The plastic may be a thermoplastic such as polyethylene, polyvinyl chloride, polypropylene, ABS, or a mixture thereof. Such composite materials are commercially available as deck materials from Trex Company, Inc of Winchester, Va.; and as Timbertech™ products from Crane Plastics Company, L.P, of Columbus, Ohio. These types of composites are described in U.S. Pat. Nos. 2,041,217; 5,474,722; 5,851,469; 5,866,264; and 6,272,808, as well as US Patent Application Publication No. 2002/0066248.
The strength and durability of natural or synthetic rubber can be improved by a vulcanizing process. In some cases sulfur is dispersed or dissolved in the rubber and then heated to create cross-links between long-chain molecules in the rubber. The process can be made more efficient by using chemical accelerators to hasten the cross-linking.
See also U.S. Pat. Nos. 1,592,591; 3,568,579; 4,681,482; 4,963,054; 5,588,775; 6,267,531; 6,551,016; U.S. Reissue Pat. RE35,380; and US Patent Application Publication Nos. 2008/0276562; 2009/0136296; 2011/0239572; and 2013/0086869.